A 12-year-old Queens boy died because his doctor wrote the wrong prescription and the pharmacy that filled it didn’t catch the obvious mistake, his heartbroken family claims in a lawsuit.

Phillipe Galette, who suffered from depression, mood swings and aggressive behavior, was a patient of Dr. Marie Gisele St. Felix at the Queens Children’s Psychiatric Center from May 2009 until his death April 2, 2010.

According to the Queens Supreme Court lawsuit, St. Felix accidentally wrote him two prescriptions for the same drug, Bupropion, at two different strengths.

Walgreens filled them both without questioning whether they were correct, the suit says.

Following the dosages on each bottle, the boy took so much of the drug that he overdosed, according to the suit filed by his adoptive mother, Pearl Pastor.

He died on the way to Jamaica Hospital.

Pastor, who is also the boy’s half-sister, said through tears, “Phillipe was very energetic. He loved life. We all miss him a lot.”

Walgreens declined comment, and lawyers for the doctor did not respond to phone messages.